In recent years, in order to achieve high breakdown voltage, low loss, and the like in a semiconductor device, silicon carbide has begun to be adopted as a material for the semiconductor device. Silicon carbide has a wide energy bandgap, high melting point, low dielectric constant, high breakdown-field strength, high thermal conductivity, and high saturation electron drift velocity compared to silicon. These characteristics would allow silicon carbide power devices to operate at higher temperatures, higher power levels, and with lower specific on-resistance than conventional silicon based power devices. Such devices must also exhibit low reverse leakage currents. Large reverse leakage currents may cause premature soft breakdown.
FIG. 1 illustrates a cross sectional view of a conventional Schottky diode, which includes ohmic contact 6, substrate 1, an epitaxial layer 2, and Schottky contact metal 5. The Schottky contact metal is made of aluminum, titanium, nickel, silver or other metals. The substrate and epitaxial layers are usually doped with N-type impurity. A Schottky junction is formed between the Schottky contact metal and epitaxial layer.
The Silicon Carbide (SiC) Schottky diode is widely accepted in recent years as it features the benefits of Schottky barrier and wide band-gap material. As a majority carrier device, it has advantages of high voltage, high speed, and low forward voltage since there is no reverse recovery current.
For pure Schottky barrier diode, a big problem is that it's surge current capability is low when compared with PN junction diode. To address this problem, junction barrier Schottky (JBS) diode or merged PN junction Schottky (MPS) diode structures were proposed.
FIG. 2 illustrates a cross sectional view of a conventional JBS/MPS diode, which includes ohmic contact 6, substrate 1, epitaxial layer 2, Schottky contact metal 5 and P-type region 4, which is usually produced by ion implantation. Is this structure, the P-type region can form PN junction which can be activated in surge condition to gain surge current capability. In general, the JBS and MPS diodes use ion implantation process to introduce the impurity region. However, ion implantation damage exists in the high-concentration impurity region formed by the ion implantation. Furthermore, the device needs high temperature process which is not compatible with silicon process, and expensive production installations and production process are required.
Therefore, there remains a need for a new and improved fabrication technique to generate the JBS and MPS diodes without ion implantation process